The yellow or pacific blue are good starter choices, the striped surgeon (clown) is a pretty big fish. I really like the yellow tangs but I do not have enough tank for one. I do like the mandarin fish and have one. I have a 10G dedicated to raising pods, it produces hundreds if not thousands. They cover the glass, crushed coral, and live rock. I have the mandarin in a 10G Nano as well. Every couple days i rotate out 3 pieces of very porous live rock (each is about about 4"x7") between this tank and my pod breeder tank. This keeps him fat and happy. I also do the same to my 40G but only about once a week seen there is not a fish in there that exclusively feeds on pods. I want to get one for my 40G as well but its hard to find one at the locals that are fat, they always get in ones that are skinny. I have the Pseudochromis porphyreus which is very close to your fridmani, great contrasting fish!! Really pops in a reef tank!! Those cardinal fish are great to, i have the spotted (PJ), very striking color and pattern when full grown. as far as the goby goes I have the yellow watchman, hides in a rock hole most of the time and darts out to get food at feeding time. Never had any blenny fish yet. That butterfly could be risky as you say, I have a risky fish as well, its a coral beauty. Had it a few months + with no issues to the reef. I have added a couple new fish since I added him and he chases them for a couple days to establish his territory but then its all fine.